Various types of motors can be used to move barriers or for other purposes. In one example, electric motors are used to move barriers such as garage doors, gates, or sliding doors. In another example, such motors are used in sump pump applications. Typically, the motor is connected to an AC power source and the AC voltage from this source is converted to a DC voltage to actually drive the motor. Sometimes, a battery backup is used when power from the mains power supply fails or is otherwise insufficient to operate the motor. In a sump pump application, water level is tracked to determine when to switch to a separate backup motor.
Different approaches have been used through the years that utilize two power sources to operate a DC motor. In one approach, a high voltage motor is selected and this motor is powered directly with the rectified mains AC voltage when the system is not in battery backup mode. When in battery backup mode, a large voltage is needed to power the high voltage motor. To generate the high voltage needed, a large number of batteries (in order to create the high-voltage) may be used. Alternatively, a small, low voltage battery and a switched-mode power supply may be used to convert the low voltage battery into a high-voltage power supply and thereby operate the motor. In either of these approaches, the cost of the system becomes high due to the requirement of large numbers of batteries or the addition of a switched mode power supply, and also the system becomes heavy and bulky with the addition of such components.
Another approach for using two power supplies with a motor utilizes a low voltage DC motor. In this case, a transformer or switched mode power supply is used to create a low voltage from the mains power source to operate the low voltage motor. In battery backup mode, the motor's operating voltage is set to match the battery voltage. However, due to the use of the transformer or switched mode power supply and the additional circuitry required, this approach is also expensive and physically heavy to implement.
Still another previous approach uses two separate motors (in two separate housing units) to move the barrier. One motor is powered directly by the rectified mains voltage source and the other motor is powered by the battery backup. However, using two motors has the disadvantage of the added expense and weight of the second motor.